golang 设置 icmp ttl

package main

import (
    "fmt"
    "net"
    "os"
    "time"
)

func main() {
    if len(os.Args) != 2 {
        fmt.Println("Usage: ", os.Args[0], "host")
        os.Exit(1)
    }
    service := os.Args[1]

    conn, err := net.Dial("ip4:icmp", service)
    if err != nil {
        fmt.Println("Error:", err.Error())
        os.Exit(1)
    }

    var msg [512]byte

    msg[0] = 8 // echo
    msg[1] = 0 // code
    msg[2] = 0 // checksum
    msg[3] = 0 // checksum
    msg[4] = 0 // identifier[0]
    msg[5] = 13 // identifier[1]
    msg[6] = 0 // sequence[0]
    msg[7] = 37 // sequence[1]

    for i := 8; i < len(msg); i++ {
        msg[i] = byte(i - 8)
    }

    // Set TTL to 100
    if err := conn.SetTTL(100); err != nil {
        fmt.Println("Error:", err.Error())
        os.Exit(1)
    }

    start := time.Now()

    _, err = conn.Write(msg[0:64])
    if err != nil {
        fmt.Println("Error:", err.Error())
        os.Exit(1)
    }

    conn.SetReadDeadline(time.Now().Add(time.Second * 5))

    var buf [512]byte
    n, err := conn.Read(buf[0:])
    if err != nil {
        fmt.Println("Error:", err.Error())
        os.Exit(1)
    }

    elapsed := time.Since(start)

    fmt.Printf("%d bytes from %s: time=%v
", n, service, elapsed)
}